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Accurate gold determination in geological samples is important for studying geological problems. Here we perform a comparative study on four desorption methods based on meta-analysis and propose a new desorption method of polyurethane foam for gold determination.

As an emerging porous crystal polymer, covalent organic frameworks (COFs) possess unique characteristics, such as high porosity, excellent stability, diverse topologies, designable open channels, and functional tunability. However, limited by the solid powder form, most COFs display low active site utilization and weak binding force with the current collector. In this pioneering research, we integrate redox-active COFs onto carbon fiber surfaces (AC-COFs) via strong covalent bridging. The 2,6-diaminoanthraquinone (DAAQ) pillars embedded on the carbon fiber surface are the key to precisely controlling the growth direction of COFs. The obtained tentacle-like array vertically supported on the surface of the carbon fiber can effectively induce charge transfer and prevent COFs from aggregating/collapsing. The strong covalent coupling and increase of accessible active sites contributed to the high specific capacitance of AC-COFs electrode (1034 mF cm

Black soils are vital agricultural resources, and assessing heavy metal contamination in black soils is of great significance to the sustainable development of agriculture and the environment. In this study, 1246 surface soil samples were collected from the central-eastern part of Changchun, where phaeozems and chernozems are widely distributed, and the As, Hg, Cr, Cd, and Pb concentrations were determined to investigate the pollution status in the black soils by the geoaccumulation index (Igeo). To eliminate the influence of background variation and improve the calculation accuracy of the Igeo values, the local background values of these five elements were estimated after classifying the samples into three clusters with the k-means clustering method. The Igeo calculated with the local background values not only identified the pollution that is difficult to recognize in the low-background areas but also eliminated the easily misidentified pollution in the high-background areas. The Igeo results show that the black soils are mainly contaminated with Hg, followed by Cd and Pb, and are almost free from the pollution of As and Cr. The further the sampling sites are from urban areas, the milder the soil pollution is. A positive matrix factorization (PMF) analysis shows that industrial activities and coal burning contributed the most to the heavy metal pollution in the black soils, followed by agricultural activities, which should be paid more attention to.

There are many Late Triassic mafic–ultramafic intrusions in the Hongqiling magmatic Ni–Cu sulfide deposit, Northeast China. Research on magma evolution leading to formation of these mafic–ultramafic intrusions is of great significance for understanding the mantle beneath Northeast China and associated Ni–Cu mineralization. A trace element study of the No. 1, 3, and 7 intrusions in the Hongqiling deposit reveals that these mafic–ultramafic intrusions are characterized by enrichment of incompatible elements, which however cannot be interpreted by subduction modification. Furthermore, model of batch partial melting of depleted mantle accompanied by upper crustal contamination can simulate the trace element patterns of these mafic–ultramafic intrusions, but partial melting of depleted mantle accompanied by lower crustal contamination model cannot work. In addition, Sr–Nd isotopic compositions of the Hongqiling No. 1, 3, and 7 intrusions also indicate that crustal contamination could have occurred mainly during the magma ascent. Consequently, a possible scenario for the magma evolution is that the primary mafic–ultramafic magma was derived from batch partial melting of a depleted mantle, and then contaminated by Cambrian–Ordovician metamorphic rocks of the Hulan Group during ascent. We conclude that the mantle source contained no significant crustal component in the Late Triassic and was also independent of substantial contribution from subducted material, and therefore the Mesozoic large-scale lithospheric delamination beneath eastern China may happen after a period of time of the Late Triassic.

Data should approach a normal distribution before application of a variety of methods for separating geochemical anomalies from background. In fact, regional geochemical data from stream sediments generally follow a skewed distribution. It is demonstrated that the skewed frequency distributions are mainly derived from mixed populations, which originate mainly from several geological sources or processes. Two kinds of regional stream sediment samples can be defined, one is a mixture of stream sediments from several lithology backgrounds, and the other is stream sediment from a single lithology background. The combination of these sample data tends to cause skewed frequency distribution. If these mixed data are processed as a whole, in other words, the multiple populations are not recognized and separated in frequency distribution, then serious errors may be made in statistical interpretation. In this study, a method for separating multiple populations is proposed from the point of view of geology, geochemistry and mathematics in an attempt to solve the problem of skewed frequency distribution. Based on the understanding that multiple populations originates mainly from differences in regional lithology background, elements that can reflect lithologies were chosen as classification indicators, then the EM algorithm was employed to separate samples from different populations, and the optimal number of populations can be reasonably determined according to geological map and mathematical indicator. This method can effectively separate multiple populations and eliminate their influence. A practical example using regional geochemical data set of stream sediments is discussed in detail to clarify the procedure.

Hexachlorocyclohexane(HCH) and Dichlorodiphenyltrichloroethane (DDT) are typical Organochlorine pesticides (OCPs), which were widely used in pest control and insect infestation in China. This study aimed at researching the concentration, potential sources and potential risk of HCH and DDT in Jilin University in Changchun, China. A total of 45 surface soil samples were collected from five land-use types in Jilin University campuses, the contents of were determined by Gas Chromatography and Mass Spectrometry (GC-MS) with Soxhlet extraction pretreatment technology. The overall HCHs existed the pollution in some campuses, while the DDTs were relatively low without pollution. Results of composition analysis showed that HCHs in campus soils mainly came from the mixed use of technical HCHs and lindane, and DDTs were mainly from the input of historical dicofol products. The potential health risks of HCHs and DDTs to campus populations were very low, while the potential ecological risks of HCHs and DDTs individual isomers should be paid attentions to.

To investigate the characteristics of lymph node (LN) metastasis of papillary thyroid carcinoma (PTC) with ultrasonography (US) and spiral computed tomography (CT) and the significance of their combination in the diagnosis and prognosis of LN metastasis.A total of 93 PTC patients admitted to and treated in the oncology department of our hospital were randomly enrolled in this study. LN imaging signs were explored by US, CT and their combination. Through the comparison with pathological findings, the diagnostic efficiency of three methods in LN metastasis in patients with PTC was analyzed. Postoperatively, all patients were followed up for 1-3 years to analyze the relationship between LN metastasis and the prognosis of PTC.Among 93 PTC patients, 69 (74.19%) had LN metastasis, and 24 (25.81%) had not. US examination revealed that metastatic LN were hypoechoic and obviously calcified, and had aspect ratio1 and strong blood flow signals. Among them, there were significant differences in calcification and blood flow between LN metastasis group and non-metastasis group (p0.05). CT images indicated that metastatic LN were swollen, had low-density and were calcified with abundant blood flow signals. In addition, the edge, calcification and CT reinforced examination showed obvious differences between the LN metastasis group and the non-metastasis group (p0.05). The sensitivity, specificity and accuracy of US alone in the diagnosis of LN metastasis were clearly better than those of CT alone (p0.05), while their combination was better than both US and CT alone in the sensitivity, specificity and accuracy in the diagnosis of LN metastasis (p0.05). Follow-up data suggested that the 3-year recurrence or metastasis rates of patients in the metastasis and non-metastasis groups were 4.54 and 11.27%, respectively, showing a statistically significant difference (p0.05).US combined with CT can make up for the deficiencies of each examination alone, and improve the sensitivity and specificity of PTC LN metastasis detection. It is worthy of clinical promotion.

Determination of types and amounts for clay minerals in soil are important in environmental, agricultural, and geological investigations. Many reliable methods have been established to identify clay mineral types. However, no reliable method for quantitative analysis of clay minerals has been established so far. In this study, an attempt was made to propose an optimization method for the quantitative determination of clay minerals in soil based on bulk chemical composition data. The fundamental principles and processes of the calculation are elucidated. Some samples were used for reliability verification of the method and the results prove the simplicity and efficacy of the approach.

Triassic mafic–ultramafic intrusions are widespread in the central-southern part of Jilin province, northeast China. Many of them are ore-bearing intrusions of considerable economic value. They compose a number of magmatic Cu–Ni sulfide deposits which are characterized by depletion of platinum-group elements (PGEs). In this study, an attempt was made to clarify the relationship between the PGE content of the mafic–ultramafic magmas and the nature and the evolution of their mantle sources. Precise PGE data of some of the typical ore-bearing intrusions are reported and the factors which may affect the PGE content of the intrusions are discussed, such as the presence of PGE in the mantle, the degree of partial melting of the mantle and the evolution of the mantle. In the course of the evolution of the mantle, a large proportion of PGE which are present as fusible components such as sulfides will be extracted, and most of the refractory PGE components such as alloys will be retained in mantle residues. Without further replenishing of PGE, later melts of a residue will contain less PGE. It is because the Triassic mafic–ultramafic intrusions are derived from PGE-depleted mantle that the magmatic Cu–Ni sulfide deposits in the central-southern part of Jilin province are reduced in PGE. We conclude that most of the young mafic–ultramafic intrusions are probably poor in PGEs.

A novel efficient blue-emitting phosphor, KMg4(PO4)3:Eu2+, was prepared by combustion-assisted synthesis method. The phase formation was confirmed by X-ray powder diffraction measurement. Photoluminescence excitation spectrum measurements show that its excitation band is extending from 250 to 420 nm. The luminescence shows a broad emission from the 4f65d → 4f7(8S7/2) transition at room temperature. Upon 289 nm light excitation, the phosphor exhibits a strong blue emission peaking at 442 nm. The doping mechanism of Eu2+ ions in KMg4(PO4)3 was discussed. The Eu2+ ions were suggested to occupy the K+ sites in KMg4(PO4)3 to induce the small crystal field splitting and weak nephelauxetic effect.